COVID nasal sprays may one day prevent and treat infection. Here’s where the science is up to

We have vaccines to boost our immunity to SARS-CoV-2, the virus that causes COVID. We have medicines you can take at home (and in the hospital) to treat COVID. Now researchers are testing something new.

They want to develop drugs that stop the virus from entering the body in the first place. These include nasal sprays that stop the virus from attaching to cells in the nose.

Other researchers are looking at the possibility of nasal sprays to stop the virus from replicating in the nose, or to make the nose a hostile site for entry into the body.

Here’s where the science is and what we can expect next.

Also read: Covid: Inhalable and nasal vaccines may offer more durable protection than regular shots

How can we block viruses?

“Viral blockade”, as the name implies, is a simple premise based on blocking SARS-CoV-2. In other words, if something gets in its way, the virus can’t attach to a cell and it can’t infect you.

Since SARS-CoV-2 is a respiratory virus, it makes sense to deliver such drugs where the virus primarily enters the body—through the nose, in a nasal spray.

Various groups around the world are working on this idea. Some research is still being conducted in the lab. Some agents have advanced to early human trials. Not yet available for widespread use.


Heparin is a common drug that has been used to thin the blood for decades. Studies in mice show that when heparin is delivered nasally, it is safe and effective in preventing virus binding to nasal cells. Researchers believe that heparin binds to the virus itself and stops the virus from attaching to the cells it is trying to infect.

A clinical trial is being conducted in Victoria in collaboration between several Melbourne-based research centers and the University of Oxford.


Covixyl-V (ethyl lauroyl arginine hydrochloride) is another nasal spray under development. It aims to prevent Covid by blocking or changing the surface of cells to prevent the virus from infecting them.

This compound has been explored for use in a variety of viral infections, and preliminary studies in cells and small animals have shown it can prevent attachment of SARS-CoV-2 and reduce overall viral load.


This molecule, which is extracted from seaweed, works by preventing viruses from entering airway cells.

A study of nearly 400 healthcare workers suggested that a nasal spray could reduce the incidence of COVID by up to 80%.


It is an engineered antibody that binds to SARS-CoV-2, preventing the virus from attaching to nasal cells.

A nasal and oral (mouth) spray is in a clinical trial to evaluate safety.

Cold atmospheric plasma

It is a gas that contains charged particles. At cold temperatures, it can change the surface of a cell.

A lab-based study shows that the gas changes the expression of receptors in the skin that normally allow the virus to attach. This results in less SARS-CoV-2 attachment and transmission.

Scientists now think this technology could be adapted to nasal sprays to prevent SARS-CoV-2 infection.

How can we stop viruses from replicating?

Another technique is to create a nasal spray that stops the virus from replicating in the nose.

Researchers are designing genetic fragments that bind to viral RNA. These fragments—known as “locked nucleic acid antisense oligonucleotides” (or LNA ASOs for short)—act a proverbial spanner and stop the virus from replicating.

A nasal spray of these genetic fragments reduces viral replication in the nose and prevents disease in small animals.

How can we change the nose?

A third strategy is to change the nasal environment so that it is less hospitable to viruses.

This may be by using a nasal spray to change the humidity level (with saline), change the pH (make the nose more acidic or alkaline), or add a virus-killing agent (iodine).

Saline can only reduce the amount of SARS-CoV-2 in the nose by washing away the virus. A study has also shown that saline nasal irrigation can reduce the severity of Covid-19. But we need more research on saline spray.

An Australian-led study found that an iodine-based nasal spray reduced the viral load in the nose. Further clinical trials are planned.

One study used a test spray – containing ingredients including eucalyptus and clove oil, potassium chloride and glycerol. The aim was to kill the virus and change the acidity of the nose so that the virus does not infect.

This novel formulation has been tested in the lab and in a clinical trial showing that it is safe and has reduced infection rates from about 34% to 13% compared to a placebo control.

obstacle ahead

Despite the promising data so far about nasal sprays for COVID, a major obstacle is keeping the sprays in the nose.

To overcome this, most sprays require multiple applications a day, sometimes every few hours.

So based on what we know so far, the nasal spray alone will not defeat Covid. But if they’re shown to be safe and effective in clinical trials, and get regulatory approval, they could be another tool to help prevent it.


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